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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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  #11  
Old 05-30-2011
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Why would your rigging be part of the electrical ground? I don't think it should be, mine isn't, and I don't think I have seen one that is.

Did hear once of an older boat where the mast was used as the negative ground for the mast lighting though - only positive wires needed that way.
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  #12  
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Quote:
Originally Posted by Hartley18 View Post
Does that make sense now??
Er... no?

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Originally Posted by Hartley18 View Post
EDIT: The above assumes the system is still negative grounded.
Illogical. If it was negative ground, it wouldn't be switched negative.

Jim
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Old 05-30-2011
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I believe the original poster has a negative ground system with the switches in the negative cable. Isn't this where we started?
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Old 05-30-2011
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Quote:
Originally Posted by SEMIJim View Post
Illogical. If it was negative ground, it wouldn't be switched negative.

Jim
Quite logical. A circuit can be switched to (negative) ground.

The switch doesn't have to be in the positive lead - it just normally is...

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Originally Posted by mitiempo View Post
I believe the original poster has a negative ground system with the switches in the negative cable. Isn't this where we started?
Maybe.. I was attempting to explain why it might have been that way originally - but that does not mean it's a good idea now. The only reason people put a switch in the positive lead is to isolate power from the entire circuit when it's switched off - for safety - no other reason at all.
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Last edited by Classic30; 05-30-2011 at 10:43 PM.
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Old 05-30-2011
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Quote:
Originally Posted by mitiempo View Post
Why would your rigging be part of the electrical ground? I don't think it should be, mine isn't, and I don't think I have seen one that is.

Did hear once of an older boat where the mast was used as the negative ground for the mast lighting though - only positive wires needed that way.
Some boats have the chainplates connected to keel bolts which forms an indirect path to ground. I didn't say anything about the brightness of the test bulb - which is irrelevant here - only that some voltage will generally exist between the rigging and battery positive. Exactly how much will depend on the construction of the boat.

In my example, it doesn't have to be the rigging - perhaps the VHF antenna shield would have been a better choice.
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Originally Posted by Hartley18 View Post
Quite logical. A circuit can be switched to (negative) ground.

The switch doesn't have to be in the positive lead - it just normally is...
Hartley18, I've been doing electrical and electronics for longer than most boats and/or their owners on this forum have been alive. I kind of rather know that

My point, which you appear to be studiously ignoring, is that it would be illogical to switch the half of the energy source that's connected to "common" or "ground" in an electrical system, not-to-mention quite possibly dangerous.

Have you ever actually seen anything, car, boat, whatever, purposely wired that way, by somebody who knew what they were doing?

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Originally Posted by Hartley18 View Post
The only reason people put a switch in the positive lead is to isolate power from the entire circuit when it's switched off - for safety - no other reason at all.
So... switches on the positive side of an energy source aren't used to remove power from the loads in order to turn them off?

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Why would your rigging be part of the electrical ground? I don't think it should be, mine isn't, and I don't think I have seen one that is.
Every last bit of metallic hardware I've seen on Abracadabra, save the stanchions, bow pulpit and stern pulpit, are bonded together. That includes all the chainplates. The shrouds and stays are metallic, and they're fastened to the "grounded" chainplates. Thus Abracadabra's rigging is "grounded." This is not uncommon at all.

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... some voltage will generally exist between the rigging and battery positive. Exactly how much will depend on the construction of the boat.
I presume you're talking about a boat with most metallic bits bonded to common "ground" and a positive ground system? True, but it should be relatively negligible. Otherwise that would tend to indicate poor connections/bonding between metallic bits.

Jim
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My mast is deck stepped. The rigging ends at chainplates which are on either the fiberglass hull or the main bulkhead. The only electrical current running in the area of the mast is for the lights on the mast. Neither of those conductors is connected to mast or rigging. It may be common but certainly cannot be relied on for troubleshooting.
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My mast is deck stepped.
So is Abracadabra.

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The rigging ends at chainplates which are on either the fiberglass hull or the main bulkhead.
Well, yeah. That's pretty typical Those plus fore and aft stays. But Abracadabra has wire running all over the place, bonding all those metal bits together.

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The only electrical current running in the area of the mast is for the lights on the mast. Neither of those conductors is connected to mast or rigging.
Perhaps I misunderstood your point. I didn't mean to suggest that the mast and rigging are part of any circuits, but only that, on many boats, they are "grounded."

Jim
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Old 05-31-2011
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Originally Posted by SEMIJim View Post
So is Abracadabra.


Well, yeah. That's pretty typical Those plus fore and aft stays. But Abracadabra has wire running all over the place, bonding all those metal bits together.


Perhaps I misunderstood your point. I didn't mean to suggest that the mast and rigging are part of any circuits, but only that, on many boats, they are "grounded."

Jim
And one of the BIGGEST mistakes folks make is to use the bonding/earth potential system as a negative return!!! Don't do it!!!! Sadly this is one thing I see ALL THE TIME.

A well known yacht designer I know said he knew his entire boat inside and out and that his electrical system was perfect. It was, until he found a fuel pump negative return circuit tied to the BONDING system and the reason the bottom paint was all funky and discolored around all of his underwater metals...

The bonding system is not designed to ever carry any current. The mast and shrouds are part of the lightning system and do not need to be "bonded" as underwater metals do.

The biggest problem with most bonding systems is that they rarely work as they are intended to because of terminal corrosion.

Switching of the positive conductor is part of the ABYC standards and a negative switched circuit will or should fail a survey if a competent surveyor is used...
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  #20  
Old 05-31-2011
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Switching of the positive conductor is part of the ABYC standards and a negative switched circuit will or should fail a survey if a competent surveyor is used...
Maine, it's interesting then that many commercial off-the-shelf bilge pump control panels (like the one below, currently fitted to my boat) are negative switched - that's one reason so many people have problems hooking them up!



1. Are you saying a commercial purpose-built product doesn't meet the standards??

2. Do you seriously expect a competent surveyor to inspect the entire wiring system on a boat - looking for circuits that might be negative switched??

No. I didn't think so.
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